INHERITANCE Chapter 6

Early Idea of Heredity “Blending Theory of Inheritance” Parents’ traits mixed in offspring

Gregor Mendel Called “the father of genetics” Pea plant study Tall vs. short…

Gregor Mendel’s Bio GhPTB5Ehttps:// GhPTB5E

Mendel & Genetics s/notes_mendel.htmlhttp:// s/notes_mendel.html Ppt of Mendel and his pea experiments (This is where the Mendel rap is.)

Mendel’s Results Mated tall plant with short plant Produced only tall plants

Mendel Tries Again Self-fertilized the offspring Tall and Short plants produced

Mendel Figures it Out! Parents pass on alleles that remain separate No blending! Particulate Theory of Inheritance

Mendel’s Peas pea-plants-helped-us-understand- genetics-hortensia-jimenez-diaz

Genes vs. Alleles Gene Height Allele: different forms of a gene Tall Short

Types of Alleles Dominant Allele: capital letter Dominant Trait: phenotype with at least one dominant allele (TT or Tt) Recessive Allele: lowercase letter Recessive Trait: phenotype with both recessive alleles (tt)

Genotype Genetic makeup Represented by letters (alleles) 2 alleles = Genotype of one trait (one allele from each parent) Ex: TT, Tt, tt

Homozygous: genotype if alleles are the same TT, tt BB,bb Heterozygous: genotype if alleles are different Tt Bb

Phenotype Appearance Determined by genotype Ex: tall, short brown eyes, blue eyes

Practice Questions 1.If having a widow’s peak is dominant, what will be the phenotype of a person with the genotype Dd?

2.If not having a cleft chin is dominant, what is the phenotype of a person with genotype aa?

3.Curly hair is dominant. What could be the following person’s genotype? HH Hh

Principle of Segregation Alleles separate during meiosis when homologous chromosomes are divided among gametes

Probability in Genetics Probability: predicts chances that certain events will occur Used to predict offspring traits

Inheritance of Alleles Monohybrid Cross: cross organisms that differ in one trait

Punnett Squares TT x tt TT t t 100% Tt = tall Tt

Tt x Tt 25% TT = Tall 50% Tt = Tall 25% tt = Short  75% Tall, 25% Short Tt T t TTTt ttTt

Monohybrid Cross Problem #1 A yellow flowered plant (Yy) is crossed with a white flowered plant (yy). What are the genotypes and phenotypes of the offspring?

Yy y y Yy yy Yyyy 50% Yy 50% yy 50% yellow 50% white

Monohybrid Cross and Punnett Squares

Dihybrid Cross Cross between two traits Pea shape and pea color

Dihybrid Cross RRYY x rryy Step 1: Find all gamete combinations Parent 1 gametes: RY, RY, RY, RY Parent 2 gametes: ry, ry, ry, ry R=round and Y=yellow

Dihybrid Cross RY ry RrYy

Phenotypes 16 Round and yellow

RrYy x RrYy Parent 1 (RrYy) RY, Ry, rY, ry Parent 2 (RrYy) RY, Ry, rY, ry R=round r= wrinkled Y=yellow y=green

Dihybrid Cross RYRyrYry RY Ry rY ry RRYYRRYyRrYYRrYy RRYyRRyyRrYyRryy RrYYRrYyrrYY rrYy RrYyRryyrrYy rryy

Phenotypes 9 round and yellow 3 round and green 3 wrinkled and yellow 1 wrinkled and green

Dihybrid Cross Practice Questions What are the gamete combinations for the genotype RrTT? RT,RT,rT,rT What are the gamete combinations for the genotype rrTt? rT,rt,rT,rt What are the gamete combinations for the genotype RrTt? RT,Rt,rT,rt

Dihybrid Cross

Principle of Independent Assortment The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes During meiosis, alleles divide independently of alleles for other characteristics

Sex Determination Sex chromosomes: X and Y Females = XX Eggs all have X Males = XY Half of sperm have X, half have Y

Polygenic Traits Traits determined by more than one gene Height Skin Color Hair Color Eye Color

EYE COLOR ed9yzM

Multiple Alleles Genes with more than 2 alleles Ex: Blood type I= makes enzyme that adds A/B to blood cell i= does not make enzyme I A I A or I A i = type A I B I B or I B i = type B I A I B = type AB ii= type O

Practice Problem If a man with the genotype ii marries a woman who is I A i, what are the genotypes and phenotypes of their offspring?

Codominance Both alleles are fully expressed Ex: Blood Type I A I B = AB blood

Incomplete Dominance No dominant or recessive alleles Both alleles are partially expressed

Incomplete dominance

Red flowered snapdragon crossed with White flowered snapdragon produces Pink flowers

Incomplete Dominance Problem Among certain flowers the allele for red flowers (R) is incompletely dominant to the allele for white flowers (r). What would be the genotypes and phenotypes of the offspring between two pink flowers?

X-Linked Traits Trait whose gene is carried only on X chromosome Expressed in males more often

Nondisjunction Nondisjunction: Failure of paired chromosomes to separate (to disjoin) during cell division, so that both chromosomes go to one daughter cell and none go to the other. Nondisjunction causes errors in chromosome number, such as trisomy 21 (Down syndrome) and monosomy X (Turner syndrome). It is also a common cause of early spontaneous abortions.

Turner’s Syndrome XO

Klinefelter’s Syndrome

Detection of Disorders:

Pedigree

Pedigrees Family tree showing genetic traits Shows genotypes and phenotypes of each family member Squares = males Circles = females Solid colored = have trait Horizontal lines = marriage Vertical lines = offspring

Sample Pedigree #1 Autosomal recessive (not X-linked) aa Aa aa Aa Aa/ AA

Sample Pedigree #2 X-linked recessive XcYXcY XcYXcY XY XcXXcX XX X c X XcXXcX

Great review PPTs for you!